1. Field of the Invention
The invention relates in general to lithographic apparatus for producing microstructures particularly for semiconductor devices.
2. Description of the Prior Art
The article entitled "Recent Advances in Electron Beam Lithography for the High Volume Production of VLSI Devices by Hans C. Pfeiffer which appears in the IEEE Transactions on Electron Devices, Vol. ED-26, No. 4, April 1979, pages 663-674 illustrates electron beam lithography devices in particular in FIGS. 3 and 4. By using a number of particle beams simultaneously, a higher output of exposed semiconductor structures can be produced than using a lithography apparatus which has only one beam which sweeps the surface to be structured in a grid-like manner. The manufacturer of semiconductor structures by means of a lithographic apparatus is described in the article published in English entitled "Design and Testing of a Corrected Projection Lens System for Electron-Beam Lithography by K. Anger, J. Frosien and B. Lischke published in the Siemens Forsch.-U. Entweickl. - Ber. Bd. 9 (1980) No. 3, Pages 174-178. Note, particularly, in this publication, FIG. 8 and the text on page 178. In the lithography apparatus disclosed by the IEEE Transactions article cited above, every individual particle beam can be deflected by applying a blanking voltage to a deflection capacitor which has electrodes mounted at the side edge relative to the particular beam generating recesses of the aperture diaphram and they are deflected to a degree such they impinge the blanking diaphragm and are thus blanked out of the further beam pass. There is a disadvantage, however, in that the beam generating recesses which have dimensions that are extremely small as compared to the dimensions of the circular area on the aperture diaphragm illuminated by the particle beam source only allow relatively low beam currents. Each diminution of the current of the beams however, leads to an increase in the time required for illumination of the areas of the resist to be exposed which receive the particle beams so that higher output which was anticipated in this apparatus as compared to the lithography apparatus using a single beam is only partially achieved.
The two articles referenced above are hereby incorporated by reference in the present application.